Fuel cell stacks which utilize gaseous reactants conventionally are provided with opposed pairs of side manifolds which distribute the reactant gases to the cells in the stack, and which gather reactant exhaust gases from the cells in the stack. In the larger commercial stacks, the manifolds may take the form of large shells which abut the sides of the stack and are secured in place by some sort of fastening means. U.S. Pat. No. 4,345,009 granted Aug. 17, 1982, is illustrative of such a commercial stack and manifold construction.
When this type of construction is used, care must be taken to seal the edges of the manifold against the stack so that the reactant gases and the exhaust gases will not escape into the ambient surroundings. This seal has been effected with elastomeric gaskets and also with elastomeric adhesive gaskets. The elastomeric gaskets rely on the compression forces of the mechanism which secures the manifold to the stack for their integrity. The elastomeric adhesive gaskets will provide a more stable seal because they rely on compressive forces plus adhesion to the stack and to the manifold for their integrity.
This invention relates to an improvement in the elastomeric adhesive seal provided by the gaskets. The improved seal will display better stability under pressure excursion conditions in the manifolds, i.e., when changes in manifold pressure occur quickly and with some degree of magnitude due to gas flow rate changes which occur in the system. These flow rate changes can result from intentional changes in operating conditions, such as, power output variations, or they can result from unintentional phenomena, such as, flow passage restriction or blockage, or the like. With the improved seal of this invention, there is formed a mechanical interlock between the sealing gasket and the manifold flange which engages the sealing gasket. The gasket used in this invention is preferably the adhesive eleastomeric gasket of the prior art, so that, as modified, the seal has the compression characteristic, the adhesion characteristic, and also a mechanical interlock characteristic. The mechanical interlock between the sealing gasket and the manifold flange is obtained by forming discreet openings in the manifold flange. These openings may be formed by drilling, milling or the like. The aforesaid openings are formed on the manifold flange which abuts the sealing gasket and is compressed by the pressure of the securement means used to hold the manifolds against the stack. The sealing gaskets are, to a certain extent, inherently flowable when placed under compression, thus, the gasket material will extrude into and flow through the flange openings as a result of the compressive forces imposed upon the gasket by the manifolds. The gaskets will thus form integral rivet-like mechanical interlocks with the manifold at each of the openings. These mechanical interlocks can only be broken if the gasket were forced by pressure to flow back out of the openings, or if the gaskets were torn at the rivet-like connectors. It is thus readily apparent that the seal formed in accordance with this invention will be more resistant to pressure-induced failure.
It is therefore an object of this invention to provide an improved seal between a fuel cell stack and associated gas manifolds mounted on the stack.
It is a further object of this invention to provide a seal of the character described wherein an adhesive sealing gasket is extruded through restricted openings in manifold flanges to form integral rivet-like connections between the gasket and the manifold.
These and other objects and advantages will become more readily apparent from the following detailed description of a preferred embodiment of the invention when taken in conjunction with the accompanying drawings.